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          canvas-剪辑、阴影和曲线绘制
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        <h3 id="剪辑"><a href="#剪辑" class="headerlink" title="剪辑"></a>剪辑</h3><figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">ctx.arc(<span class="number">300</span>, <span class="number">100</span>, <span class="number">200</span>, <span class="number">0</span>, <span class="built_in">Math</span>.PI * <span class="number">2</span>, <span class="literal">true</span>) <span class="comment">// 剪辑的区域</span></span><br><span class="line">ctx.clip() <span class="comment">// 剪辑</span></span><br><span class="line">ctx.fillStyle = <span class="string">&#x27;red&#x27;</span></span><br><span class="line">ctx.fillRect(<span class="number">100</span>, <span class="number">100</span>, <span class="number">200</span>, <span class="number">200</span>)</span><br></pre></td></tr></table></figure>

<img src="http://blogs-images.youchen-blog.cn/Snipaste_2020-08-31_21-46-30.png" style="zoom:33%;" />

<p><strong>注：</strong> 可以通过 <code>ctx.save()</code> 和 <code>ctx.restore()</code> 来恢复环境</p>
<h3 id="阴影"><a href="#阴影" class="headerlink" title="阴影"></a>阴影</h3><figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">ctx.shadowOffsetX = <span class="number">10</span></span><br><span class="line">ctx.shadowOffsetY = <span class="number">10</span></span><br><span class="line">ctx.shadowColor = <span class="string">&#x27;grey&#x27;</span></span><br><span class="line">ctx.shadowBlur = <span class="number">10</span></span><br><span class="line">ctx.fillStyle = <span class="string">&#x27;red&#x27;</span></span><br><span class="line">ctx.fillRect(<span class="number">100</span>, <span class="number">100</span>, <span class="number">100</span>, <span class="number">100</span>)</span><br></pre></td></tr></table></figure>

<img src="http://blogs-images.youchen-blog.cn/Snipaste_2020-08-31_21-58-50.png" style="zoom:33%;" />

<h3 id="贝塞尔曲线"><a href="#贝塞尔曲线" class="headerlink" title="贝塞尔曲线"></a>贝塞尔曲线</h3><figure class="highlight js"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">ctx.beginPath();</span><br><span class="line">ctx.moveTo(<span class="number">150</span>, <span class="number">250</span>);</span><br><span class="line">ctx.quadraticCurveTo(<span class="number">239</span>, <span class="number">89</span>, <span class="number">450</span>, <span class="number">250</span>);</span><br><span class="line">ctx.stroke();</span><br></pre></td></tr></table></figure>


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